4.44. Effluents from metal-finishing plants have the potential of discharging undesirable quantities of metals, such as cadmium, nickel, lead, manganese, and chromium, in forms that are detrimental to water and air quality. A local metal-finishing plant has identified a wastewater stream that contains 5.15 wt% chromium (Cr) and devised the following approach to lowering risk and recovering the valuable metal. The wastewater stream is fed to a treatment unit that removes 95% of the chromium in the feed and recycles it to the plant. The residual liquid stream leaving the treatment unit is sent to a waste lagoon. The treatment unit has a maximum capacity of 4500 kg wastewater/h. If wastewater leaves the finishing plant at a rate higher than the capacity of the treatment unit, the excess (anything above 4500 kg/h) bypasses the unit and combines with the residual liquid leaving the unit, and the combined stream goes to the waste lagoon. m(kg Cr/h) [no water] 95% of Cr in feed to unit Wastewater m,(kg/h) 0.0515 kg Cr/kg m(kg/h) < 4500 kg/h is(kg/h) m(kg/h) m;(kg/h) To waste lagoon a. Without assuming a basis of calculation, draw and label a flowchart of the process. b. Wastewater leaves the finishing plant at a rate m1 Cr/kg). 6000 kg/h. Calculate the flow rate of liquid to the waste lagoon, m6(kg/h), and the mass fraction of Cr in this liquid, x6(kg Answer c. Calculate the flow rate of liquid to the waste lagoon and the mass fraction of Cr in this liquid for m, varying from 1000 kg/h to 10,000 kg/h in 1000 kg/h increments. Generate a plot of x6 versus m1.- (Suggestion: Use a spreadsheet for these calculations.) d. The company has hired you as a consultant to help them determine whether or not to add capacity to the treatment unit to increase the recovery of chromium. What would you need to know to make this determination? e. What concerns might need to be addressed regarding the waste lagoon?

F1 F2 A2 P2 The following is known: Area, A1= 0.3 ft and A2= 7.6 A1- Assuming an incompressible fluid If a force F1 of 44.3 lbf / ft2 is applied at (1) then the resultant force, F2 in Ibf is equal to -- ?

A U-tube manometer is connected between two pipes as shown below. One pipe contains carbon tetrachloride at 13 kPa gauge, while the other pipe contains oil at 172 kPa absolute. Determine the height, h, in mm. Assume barometer reads 0.9 atm. Carbon tetrachloride SG = 1.6 4m Oil SG 0:8 h

1) Pavithran Ravindran explains to a group of inspiring CBE students that the Reynolds number is a dimensionless group defined for a fluid flowing in a pipe as Re = Dvp/µ where D = pipe diameter, v = average fluid velocity, p = fluid density, and u = fluid viscosity. When the value of the Reynolds number is less than about 2100, the flow is laminar -- the fluid flows in smooth streamlines. For Reynolds numbers above 2100, flow is turbulent -- a great deal of internal agitation takes place. %3D Methyl ethyl ketone (MEK) flows through a 2.067-in. ID pipe at 20°C, at which temperature its density is 0.805 g/cm³ and its viscosity is 0.43 centipoise (1 centipoise = 1.00 x 10-3 kg/m.s). The average fluid velocity is 0.048 ft/s. Determine whether the flow is laminar or turbulent. %3D